PROJECT SUMMARY Patients with metastatic non-small cell lung cancer (NSCLC) remain incurable with few options. New therapies are critically needed. In this project we propose to translate a fundamental understanding of microRNAs (miRNAs) in NSCLC. The EGFR/RAS and p53 pathways are the most frequently dysregulated pathways in NSCLC and are regulated in part by two miRNAs, miR-34 and let-7, tumor suppressors that regulate key lung cancer oncogenes such as KRAS and are lost or poorly expressed in many lung tumors. miR-34 is directly up- regulated by p53 and is one of the most important outputs of p53 signaling. We will test the hypothesis that a novel miRNA-based therapeutic strategy focused on miR-34 reverses NSCLC tumor phenotypes. Preliminary data generated from our lab shows that MRX34, a nanoparticle encapsulated mir34 molecule, provides a benefit in Kras and in Kras;p53 mutant NSCLC mouse models. Our goal is to evaluate MRX34 in patients with metastatic NSCLC while incorporating novel imaging methods to determine drug delivery and effect. In Specific Aim 1 we will investigate miR-34 therapeutics in NSCLC mouse models. We have preliminarily shown that miR-34 administered to KRAS or KRAS;p53 mutant tumor cells blocks proliferation and induces apoptosis, including when delivered systemically as MRX34 to Kras or Kras;p53 mutant mouse models. We propose to investigate efficacy and optimal dosingand scheduling of MRX34 using mouse models; test the effects of MRX34 in combination with drugs known to be active against NSCLC in vitro in KRAS; p53 NSCLC cell lines and in vivo and test if MRX34 treatment shows therapeutic potential in EGFRL858R;p53, and erlotinib- resistant EGFRT790M;p53 mutant mice (in collaboration with Dr. Katie Politi [Project 3]). In Specific Aim 2 we will investigate if MRX34 is delivered to the appropriate tissues and engages its targets. We propose to discover serum and tumor biomarkers in the Kras and Kras;p53 mutant mice treated with MRX34 that will be useful for PK, PD, and efficacy analyses in the clinical trial proposed in Aim 3; to apply 18F-ICMT-11 PET imaging of caspase-3 to measure MRX34-induced apoptosis in lung tumors in Kras;p53 mice. We will radiolabel MRX34 particles with F-18 and if successful, incorporate this as an imaging endpoint to validate magnitude and kinetics of particle delivery to in these models. In Specific Aim 3 we will conduct a clinical trial with MRX34 in patients with NSCLC preselected based on genotype, evaluating response/efficacy and PD endpoints to assess drug delivery and drug:target effects using both novel imaging tools developed in Aim 2 (18F-labelled MRX34 nanoparticle) as well as direct tumor signal transduction effects using 18F-ICMT-11 (caspase) as an exploratory biomarker for drug-induced apoptosis. Patient biopsies will be genotyped for the KRAS, EGFR and p53 status, and tumor and serum miR-34 (and let-7) levels determined. These data will be correlated with outcome and could inform patient selection in these and future trials.